The Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (UTRAN) is a radio network of a UMTS system which is one of the third-generation (3G) mobile communication technologies, which was designed to succeed GSM.
Evolved UMTS Terrestrial Radio Access Network (E-UTRAN, also referred to as LTE (Long Term Evolution)) is standardized by 3GPP Long Term Evolution (LTE) which is a project within the 3rd Generation Partnership Project (3GPP) to improve the Universal Mobile Telecommunication System (UMTS) standard with High Speed Packet Access functionality to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, lowered costs etc. An E-UTRAN typically comprises user equipments (UE) 202 wirelessly connected to radio base stations 204a-c as illustrated in FIG. 1. In the E-UTRAN, the radio base stations 204a-c are directly connected to the core network (CN) 203 e.g. to a MME (Mobility Management Entity). In addition, the radio base stations 204a-c are also connected to each other via an interface. The radio base stations are usually referred to as NodeB in UTRAN and to eNodeB in E-UTRAN. Furthermore, a home radio base station 201 denoted Home eNode B (HeNB) may be connected to the core network, either directly to MME/SGW (Serving Gateway) or indirectly via a gateway node. A HeNB is a radio base station having a reduced coverage adapted to be used in a home environment, implying a reduced power consumption.
The LTE concept also includes the possibility to have an E-UTRAN radio base station serving at least one LTE femto cell to provide home or small area coverage for a limited number of users, e.g. a family. This type of radio base station is referred to as Home eNodeB (HeNB) in this specification.
The HeNB would provide normal coverage for the end users and would be connected to the mobile core network and/or Gateway using some kind of IP based transmission. The coverage provided is called femto cell in this document.
One of the main drivers of this concept of providing Local Access is to provide cheaper call and/or transaction rates/charges when connected via the HeNB compared to when connected via the eNBs of the macro radio network. Another driver is improved capacity for a user since the HeNB may provide dedicated service to one user or to a very limited number of users.
The HeNB is usually connected to the mobile core network and possibly to other HeNB or eNB via the end user's existing broadband connection (e.g. xDSL, Cable).
In order to achieve access control to the HeNB, the concept of HeNB White-list has been introduced. The HeNB White-list comprises Closed Subscriber Groups, CSG ids (e.g. cell identity) of the HeNBs which the UE is authorized to access. The UE reads the broadcasted system information in a cell and can identify that the cell is a femto cell. The UE can then read a global cell identity such as the unique “Long Cell Identity” (which comprises for example PLMN-id, Tracking Area Id and Cell Id or only PLMN-id and Cell Id or only the Cell Id) of the femto cell, to further check towards to contents of the HeNB White-list to find out whether the UE is allowed to access that specific femto cell. This means that the HeNB White-list for a specific UE should comprise a number of “Long Cell Identities” for the femto cells that this UE is authorized to access. The main advantage is that the UEs can avoid performing unnecessary access attempts to HeNBs that the UE is unauthorized to access. The list may be transferred to the UEs by dedicated signaling or e.g. initially configured during a pairing procedure.
It has also been discussed in 3GPP that the MME of the core network should be able to reject e.g. a Tracking Area Update or a Service Request from an UE accessing via a HeNB that the UE is not allowed to use. This means that the MME has access to an Access Control Database which contains information about the UEs that are authorized to access a specific HeNB (e.g. identified by an HeNB-id). The UEs may be identified with e.g. the IMSI (International Mobile Subscriber Identity).